Let's talk a bit about Lord Oress. And how much he sucks.
Basically, this guy is one endless case of Napoleon Syndrome. He's shorter than his wife, his children(except for Tezanna) and besides that, he has so many inadequacy issues stemming from the fact that when he married Caterina, he was considered lower than her, so her had to change his surname to Oress instead of her changing to his.
Then after three wonderful Force-sensitive sons, all of whom are as blessedly handsome as him(not my words, his), Caterina has a daughter who.. doesn't look like either of them. He's not happy. Not only that, the baby that is so obviously not his isn't Force-sensitive.
Which leads to so much more assholery with Elessabeth's upbringing, but we're not going there, let's just say he did some awful things to her.
He doesn't find out the identity of his wife's lover for some time, and sends an Imperial Intelligence agent to eliminate the man and the embarassing evidence.
Then, years later, his only surviving child gets married to a man he didn't approve and his first reaction is to try and have him killed.
Long story short, it's no wonder his wife and daughter murdered him.